|(Average width = 3.1 m / 10.3 ft)||Source: Rails-to-Trails Conservancy|
|(Average = 10.1 m / 33 ft)||Source: Rails-to-Trails Conservancy|
The term "setback" refers to the distance between the edge of an RWT and the centerline of the closest active railroad track while "separation" refers to the treatment of the space between an RWT and the closest active railroad tracks, including fences, vegetation, ditches, and other items (see Figure 5.6). When determining the minimum setback for a RWT, factors to consider include train speed and frequency, maintenance needs, applicable State standards, separation techniques, historical problems, track curvature, topography, and engineering judgment.
The range of trail setback on the existing RWTs varies from less than 2.1 m (7 ft) to as high as 30 m (100 ft) (see Figure 5.7), with an average of almost 10 m (33 ft) of setback from the centerline of the nearest track. A comparison of RWT setback distance to both train speed and frequency reveal little correlation; over half (33 of 61) of the existing RWTs have 7.6 m (25 ft) or less setback, even alongside high speed trains (see Figures 5.8 and 5.9). Many of the trails with little setback are ones that have been established many years. The trail managers for these well-established trails report few problems. However, interviews with train engineers in several areas indicate that they observe a tremendous amount of daily trespassing and problems in areas with little setback and no physical separation.
In comparison, RWTs in Perth, Australia, are typically 3 m (10 ft) wide, and separated from the adjacent railway line by a 1.8 m (6 ft) high chain link fence with three strands of barbed wire. The minimum setback from track centerline to the fence is 4.5 m (15 ft).
Researchers attempted to determine if narrower setback distances have a direct correlation to safety problems. However, based on the almost nonexistent record of claims, crashes, and other problems on any RWTs, they were unable to determine a correlation between setback distance and trail user safety. An FRA study on the impact of high train speed on people standing on boarding platforms concludes that induced airflow is a safety issue for a person within 2 m (6.5 ft) of a train traveling at 240 km/h (150 mi/h) (Volpe, 1999).
There is no consensus on either appropriate setback requirements or a method of determining the requirement. Some trail planners use the AASHTO Bike Guide for guidance. Given that bicycle lanes are set back 1.5 to 2.1 m (5 to 7 ft) from the centerline of the outside travel lane of even the busiest roadway, some consider this analogous. Others use their State Public Utilities Commission's minimum setback standards (also known as "clearance standards") for adjacent walkways (for railroad switchmen). These published setbacks represent the legal minimum setbacks based on the physical size of the railroad cars, and are commonly employed along all railroads and at public grade crossings. The minimum setback distance is typically 2.6 m (8.5 ft) on tangent and 2.9 m (9.5 ft) on curved track. However, FRA and railroad officials do not consider either of these methods to be appropriate for an RWT. This is because AASHTO's guidelines for motor vehicle facility design are not seen as comparable to rail design, and the setback distance for the general public should be much greater than that allowed for railroad workers.
FIGURE 5.8 RWT setback/train speed correlation
FIGURE 5.9 Setback/frequency correlation
Some railroads and States have established their own standards. For example, the BNSF's policy on "Trails with Rails" states, "Where train speeds are greater than 145 km/h (90 mi/h), trails are not acceptable. No trail will be constructed within 31 m (100 ft) of any mainline track where train speeds are between 113 km/h (70 mi/h) and 145 km/h (90 mi/h). Trails may be constructed between 15 m (50 ft) and 30 m (100 ft) where mainline train speed is 80 km/h (50 mi/h) to 113 km/h (70 mi/h). Trails may be constructed 15 m (50 ft) from centerline of track where train speeds are 40 km/h (25 mi/h) to 80 km/h (50 mi/h), and 9 m (30 ft) from any branchline track with speeds of 40 km/h (25 mi/h) or less. No trails less than 9 m (30 ft) from centerline of track for any reason." The Alaska Railroad Corporation rule of thumb for setbacks along main tracks is one railcar length, or 18 to 21 m (60 to 70 ft), unless careful analysis of the risks suggests otherwise. In contrast, the Maine Department of Transportation allows for trails to be set back a minimum of 5.5 m (18 ft) from track centerline, down to 4m (12.5 ft) in constrained circumstances. Other considerations when determining setback may be flying debris and maintenance access. Trains throw up debris from the roadbed, including rocks and other objects deliberately placed on the rails by trespassers. Fast-moving trains have thrown up large ballast rocks. Debris has been known to fall off trains, or, in some cases, to hang off rail cars. Railroad companies need access to tracks for routine and emergency maintenance, including tie and ballast replacement, cleaning culverts, and accessing switches and control equipment. While most railroad companies have the ability to maintain tracks from the tracks themselves, it often is more cost effective and less disruptive to access the tracks from maintenance vehicles operating alongside the tracks. At a minimum, railroads need at least 4.5m (15 ft) from the track centerline to provide reasonable access to their tracks.
Further considerations when determining setback requirements may be physical constraints on or adjacent to railroad corridors, presence of separation techniques such as fencing, historical trespassing, and other problems. Finally, train densities can change at any time and location, and railroads require flexibility in their operations to meet customer requirements. Structures or right-of-way modifications that impede a railroad's ability to change or control its operations are unacceptable.
Because of the lack of consensus on acceptable setback distances, the appropriate distance must be determined on a case-by-case basis (see Figure 5.10). Trail planners should incorporate into the feasibility study analysis an analysis of technical factors, including:
Another determining factor may be corridor ownership. Trails proposed for privately-owned property will have to comply with the railroad's own standards. Trail planners need to be aware that the risk of injury should a train derail will be high, even for slow-moving trains. Discussions about liability assignment need to factor this into consideration.
In many cases, adequate setback widths, typically 7.6 m (25 ft) or higher, can be achieved along the majority of a corridor. However, certain constrained areas will not allow for the desired setback width. Safety should not be compromised at these pinch points ? additional barrier devices should be used, and/or additional right-of-way purchased. In the case of high speed freight or transit lines, RWTs must be located as far from the tracks as possible and are infeasible if adequate setbacks and separation cannot be achieved.
FIGURE 5.12 Minimum RWT setback - fill sections (depending on situation)
FIGURE 5.13 Minimum RWT setback - constrained sections (depending on situation)
At an absolute minimum, trail users must be kept outside the "dynamic envelope" of the track - that is, the space needed for the train to operate (see Figure 5.11). According to the MUTCD (Section 8), the dynamic envelope is "the clearance required for the train and its cargo overhang due to any combination of loading, lateral motion, or suspension failure." It includes the area swept by a turning train.
Relatively narrow setback distances of 3 m (10 ft) to 7.6 m (25 ft) may be acceptable to the railroad, RWT agency, and design team in certain situations, such as in constrained areas, along relatively low speed and frequency lines, and in areas with a history of trespassing where a trail might help alleviate a current problem. The presence of vertical separation or techniques such as fencing or walls also may allow for narrower setback.